Technical Field
The technology of the present application relates to an exhaust heat recovery system.
Related Art
There are technologies that use exhaust heat from an engine to raise the temperature of engine coolant. For example, Japanese Patent Application Laid-open (JP-A) No. 2015-145663 discloses a technology that recovers, by means of an exhaust heat recovery unit disposed in an exhaust pipe, heat from exhaust gas and utilizes the heat for space heating and to promote the warmup of the engine, with the technology adjusting the recovery amount of the exhaust heat on the basis of a travel history in order to prevent or control freezing inside the exhaust pipe.
Specifically, JP-A No. 2015-145663 discloses a structure where a bypass path that bypasses the exhaust heat recovery unit is disposed in a coolant circulation path, so that the structure has a circulation flow path that passes through the exhaust heat recovery unit and a circulation flow path that does not pass through the exhaust heat recovery unit. Additionally, by using a switching valve to switch between the two circulation flow paths, the amount of the coolant circulating to the exhaust heat recovery unit is adjusted and the recovery amount of the exhaust heat is adjusted. JP-A No. 2015-145663 discloses that, by controlling the opening degree of the switching valve, the switching valve may control whether or not to allow the coolant to flow to the exhaust heat recovery unit and may control the flow rate of the coolant flowing to the exhaust heat recovery unit.
Furthermore, JP-A No. 2015-145663 discloses that the coolant is circulated by a water pump to the exhaust heat recovery unit, and the flow rate of the coolant flowing to the exhaust heat recovery unit is adjusted by controlling the water pump.